Should the `if (this != &rhs)` Check Be Included in a Move Assignment Operator?

Move Assignment Operator and if (this != &rhs)

In the assignment operator of a class, it is a common practice to check if the object being assigned is the invoking object to avoid potential errors. This is done using the condition if (this != &rhs).

However, in the context of the move assignment operator, specifically when the right-hand side (RHS) is an rvalue reference (such as Class&&), there is a question as to whether this check is necessary.

Some argue that the check is not required because an rvalue reference always refers to a unique, temporary object that cannot be aliased elsewhere. In this case, this != &rhs is always true.

Others argue that the check is still advisable as a defensive measure, even though it is not strictly required by the standard. They assert that it provides an additional guarantee and prevents potential bugs or undefined behavior if the client code mistakenly passes a self-reference.

The general consensus seems to be that the check is not strictly necessary in the context of move assignment, but it is not harmful either. If the move assignment is implemented using the popular Copy and Swap idiom, it is common practice to include the check. However, if the move assignment is implemented without Copy and Swap, the check may be omitted.

Ultimately, the decision of whether or not to include the check is a matter of personal preference and design considerations.

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